Wilhelm, M., de Lacroix, S. F., Titman, J. J., Schmidt-Rohr, K., & Spiess, H. W. (1993). THE ORIENTATION DISTRIBUTION IN AN INDUSTRIAL-SAMPLE OF POLY(P-PHENYLENETEREPHTHALAMIDE) DETERMINED BY 2-DIMENSIONAL AND 3-DIMENSIONAL NMR TECHNIQUES. Acta Polymerica, 44(6), 279-284. doi:10.1002/actp.1993.010440604.